In a projection video display, geometric raster distortions result from the physical placement of the cathode ray display tubes. Such raster distortions are exacerbated by the use of cathode ray tubes with curved, concave phosphor surfaces and the inherent magnification in the optical projection path. The projected image is composed of three scanning rasters which are required to be in register one with the other on a viewing screen. The precise overlay of the three projected images requires the adjustment of multiple waveforms to compensate for geometrical distortion and facilitate the superimposition of the three projected images. However, manual alignment of multiple waveforms is labor intensive during manufacturing, and without the use of sophisticated test equipment may preclude setup at a user location. An automated convergence system simplifies manufacturing alignment and facilitates user location adjustment by using raster edge measurement at peripheral display screen locations to determine raster size and convergence. Such an automated convergence system relies on sensors, located at screen edge locations, being illuminated by a projected setup marker M. The intensity of illumination at each sensor may vary greatly for a number of reasons as discussed in U.S. Pat. No. 6,392,612 titled Opto Sensor Signal Current Detector which is hereby incorporated by reference. Thus to avoid generating erratic signals from weak or poorly illuminated sensors it is advantageous to apply differing amounts of detection sensitivity in the form of a sensor signal detection threshold. To reduce alignment time an accelerated sequence is required where detection sensitivity differences are controllably selected in accordance with the color of the projected setup marker image